The present invention relates to a stationary supporting structure comprising a column consisting of prefabricated superjacent elements and a vertical central steel tube extending through throughgoing apertures in the elements, the adjacent elements having mating concave and convex, respectively, spherical bearing surfaces. The structure preferably comprises a plurality of interconnected columns of this type, but the principles according to the invention may also be used in the construction of a single column if desired. The structure is especially advantageous in the construction of a platform or the like resting on the sea bed, but positioned above the sea level, such as platforms for the production of oil from the sea bed. However, the supporting structure may also advantageously be used for other structures such as bridges or the like if there are difficulties connected with the erection of a suitable formwork for a concrete column.
Known platforms having a supporting structure resting on the sea bed, the platform itself being positioned substantially above the sea level (in the North Sea at least 20 m), are huge and expensive due to the difficulties connected with the production thereof, especially in relatively deep waters, such as 60 to 70 m or more. It is known to errect certain concrete structures at the coast and then float the structures to the required position, where they are lowered and placed on the sea bed. An example of such a structure is the oil storage tank installed at the Ekofisk field in the Norwegian sector of the North Sea. Hollow concrete columns which may be used e.g. to support platforms may be produced in a similar way as the Ekofisk tank, the columns being subsequently floated to the erection site and positioned on the sea bed. Since, in connection with such platforms the diameter of the columns may be in the order of 5 m, the columns are very large and heavy and consequently difficult to manoeuvre.